Add scoped lifetime to DI - inject the same service instance to child components

[Andrzej-W]

Let's assume I have a Customer component - this is the parent component. I also have CustomerList and CustomerDetails components - these are child components and they are displayed inside Customer component. All three components have to share some data and some business logic including Web API calls. I want to encapsulate this in CustomerService. Currently the only reasonable choice is to register CustomerService as Singleton and then inject it into all three Customer* components.

It's OK but below is another scenario where Singleton is not enough.

I have CustomerComparer component and I want to display two different customers side by side. To do this I want to use two Customer components. Of course they cannot work with the same instance of CustomerService. The only solution I see here is to register CustomerService as Scoped (which is currently equivalent to Singleton). Scoped should work as follows:

• service injected into the first component in hierarchy should work as Transient,
• all child components should get the same service instance as parent component.

With the above functionality I will be able to display two Customer components at the same time.

Look at #5496 also.

[SteveSandersonMS]

We would probably handle this by a mechanism like context in #5455 rather than DI. There are often situations where you'd want to share state with a subtree without having to register things in DI, and once we enable that, you wouldn't need the DI approach. Hope that makes sense!